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Max side load of a 20 inch rim?
I was wondering what the max load (side) is of a 20 inch wheel, for that
matter the side load of a 24 and 26 would be good too. Ben |
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#2
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Max side load of a 20 inch rim?
Hummm, good point, but is there a starting point for say a standard BMX rim
and one for a standard Mountain Bike rim? Please dont ask me what is standard... lets start with a Walmart cheapie rim and I will go from there. Ben "Jeff Wills" wrote in message om... "Ben" wrote in message news:6OGzc.46610$Ds.46416@clgrps12... I was wondering what the max load (side) is of a 20 inch wheel, for that matter the side load of a 24 and 26 would be good too. Ben Excellent question. However, there's a lot more variables than just size. For instance: Rim width Rim cross-section Rim material Spoke tension Number of spokes Spoke bracing angle ... and a few more than I've probably missed. Jeff |
#3
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Max side load of a 20 inch rim?
I really must work on how I word things and be explicitly specific
I am looking for a good guess (if not exact numbers) of the maximum side load a bike wheel (preferably a cheap 20" bmx wheel) can take before becoming a pretzel (i.e catastrophic failure and or but not including warping). This includes but is not limited to (ha-ha) nuts, washers, axel, axel bearings, bearing keepers, hub, spokes (likely 32 in total), spoke nipples (32 to match previous item), rim, rim rubber band to keep the nipples from the tube, tube (if used, if not strike last comments, preferably a standard tube not a shrader valve tube), and tire (preferably a slick as it is a road bike). One more thing, I will be using 14mm and above size axles before this deviates us from the current question leading us into many many debates on stuff other than the question at hand. What I am trying to do here is design a frame (trike) and on the rear axel (two wheels on this axel, maybe a bad choice of words here again 'on the rear weldment assembly, which are attached 2 axels') figure out the necessary strength of the rear weldment assembly. These wheels (on the rear weldment assembly) do not lean, they will be vertical at all times and should I hit a turn at a high rate of speed. I know approximately how many G's I generate on this said high rate of speed turn, I want to know how much the wheel will take before warping. I then will take this data and build the frame to take the side load the wheel can, using appropriate safety factors. Before I get a lecture on the theories on design and that I may be over my head in this, I am a experienced aircraft designer and have FEA and CFD tools to help me in this venture as well as experience in doing the calcs by hand. I am not trying to be smart here I just want to be specific so I can find out a resource of side loading capabilities of a bike wheel or how to calculate it without having to rig up a test and determine it my self. Ben "Jeff Wills" wrote in message om... Any starting point is irrelevant if you're just asking about the rim. A spoked wheel's strength is in the tension of the spokes. If you want resistance to side loads and only want to compare rims, wider is better, thicker is better, and aluminum is better. Larger diameter wheels will be weaker. Beyond that, you're on your own. Jeff "Ben" wrote in message news:rpYzc.48217$Ds.46630@clgrps12... Hummm, good point, but is there a starting point for say a standard BMX rim and one for a standard Mountain Bike rim? Please dont ask me what is standard... lets start with a Walmart cheapie rim and I will go from there. Ben "Jeff Wills" wrote in message om... "Ben" wrote in message news:6OGzc.46610$Ds.46416@clgrps12... I was wondering what the max load (side) is of a 20 inch wheel, for that matter the side load of a 24 and 26 would be good too. Ben Excellent question. However, there's a lot more variables than just size. For instance: Rim width Rim cross-section Rim material Spoke tension Number of spokes Spoke bracing angle ... and a few more than I've probably missed. Jeff |
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Max side load of a 20 inch rim?
"Ben" wrote in message
news:7s0Ac.45932$eA.1307@clgrps13... I really must work on how I word things and be explicitly specific I am looking for a good guess (if not exact numbers) of the maximum side load a bike wheel (preferably a cheap 20" bmx wheel) can take before becoming a pretzel (i.e catastrophic failure and or but not including warping). ... I am not trying to be smart here I just want to be specific so I can find out a resource of side loading capabilities of a bike wheel or how to calculate it without having to rig up a test and determine it my self. It's got to be easier to pick up a kid's/BMX bike at the dump Saturday morning, clamp the axle to something solid and load the thing to failure. Your test rig is just the something solid, a bathroom scale, and a tape measure. Because you don't really have any idea how it will fail (rim, spokes, axle, housing, etc.), you're wasting your time speculating. One bike gives you two wheels, and by the time you break them, you'll be a real world expert on lateral loading of trike tires. My guess is that your trike rear axle support will be stiffness-limited, and the structure you build to get decent, safe handling will be far stronger than you need to resist "catastrophic failure." free advice, Fred |
#5
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Max side load of a 20 inch rim?
"Ben" wrote in message
news:7s0Ac.45932$eA.1307@clgrps13... I really must work on how I word things and be explicitly specific I am looking for a good guess (if not exact numbers) of the maximum side load a bike wheel (preferably a cheap 20" bmx wheel) can take before becoming a pretzel (i.e catastrophic failure and or but not including warping). ... I am not trying to be smart here I just want to be specific so I can find out a resource of side loading capabilities of a bike wheel or how to calculate it without having to rig up a test and determine it my self. For most wheels the correct spoke tension is slightly above 100 kg force. Somewhat above this loading the rim cannot correctly support the loads and crinkles. If the load is uneven across spokes the spokes can pull through the hub flange. The spokes themselves do not break until considerably higher loadings are reached. See The Book for more detail. So: take your intended wheel, count the spokes and measure the spoke angle from flange to rim. Simple trig will show you how much tension there is to support the rim against a side load. I'd expect that a 48-spoke BMX wheel with a wide hub would withstand side loads at least as well as anything else commonly encountered in the bike world. -- "Do stairs, stairs, and more stairs, wherever you can find them." - Jim Roberts in rec.backcountry |
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Max side load of a 20 inch rim?
On Wed, 16 Jun 2004 18:37:55 GMT, Ben wrote:
should I hit a turn at a high rate of speed. I know approximately how many G's I generate on this said high rate of speed turn, I want to know how much the wheel will take before warping. I then will take this data and build the frame to take the side load the wheel can, using appropriate safety factors. Surely you're limitted by friction to a sufficiently low number that teh design of lateral strength is not particularly significant - ruggedness would be more of a criterion? That is, assuming you're not going so fast that you develop any aerodynamic down-force, and assuming you don't have tacky tyres (both reasonable assumptions, I think), you can't get more than your combined body & vehicle weight vertical force on a wheel (other than transients) and you won't get a coefficient of friction more than 1, so say, design it for 120kg transverse force (unless you're particularly heavy). I don't think transients will generate transverse loads, because I think the tyre will flex (in a roll-off-the-rim type way) when subject to transient transverse loads, and such a transient will not get to teh frame. regards, Ian SMith -- |\ /| no .sig |o o| |/ \| |
#7
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Max side load of a 20 inch rim?
I live in Canada (Ontario) too so will use Cdn prices and all the parts are
available from Toronto, to BC and Montreal. First, I use standard 20", 48 spoke BMX wheels with 14mm axles that can be bought anywhere from about $15 wholesale up to about $100. I don't know what the spoke tension is because I buy the rims already assembled, and I've never had a wheel fail, or heard of one of these wheels fail, on a trike yet. I undo the wheel, jam and bearing nuts and shift the axles over to one side as far as they can go. This is usually in the range of having about 1.75" to 2" of axle sticking out past the bearing/jam nuts on one side. To secure the axles to the bottom of the king pins, I use plain old 3/4" ,ild steel tubing with 1/8" thick wall. I cut a piece about 1.25" long and weld it (both MIG and TIG) at the appropriate angle to the bottom of the king pin bolt. I take a 35/64" drill bit (I don't have a 14mm drill bit ) and drill out the center to accept the 14mm axle. Just about a perfect fit. As for strength and wheel security/tightness: - my brother is 6'4" and weighs 265lbs. He rides my trikes all the time and the wheels are fine - a friend is 6'1", weighs 260lbs and he puts the trikes up on two wheels and rides them around like that just about daily. He says it's a "crowd pleaser" - I am 6'2", weigh ~235lbs and ride fast and hard most of the time. I have taken 90 degree road corners on narrow 2 lane roads at ~45kph - no problems at all. I also ride the trikes around occasionally on 2 wheels, sometimes at speeds approaching 30kph. Again, no problems. - we all have ridden the trikes to relatively high speeds (approaching 75kph) and our roads and sidewalks are not always as smooth and crack/pothole free as they could be. While I have to watch the wheel's axle nuts to make sure they stay tight (I use red and blue Loctite), I have never had an axle housing stretch/deform on me, I have never had an axle bend or break. The 48 spoke 20s might flex 1/4" when riding hard corners or up on two wheels. They're very tough it would seem. I never hear the spokes clicking or pinging and I would think that those kinds of noises would be evidence of rim deformation or wheel problems (not an engineer - so don't quote me on that). The only things I worry about are the 26" rear wheels. Again though, they are standard steel and aluminum 36 spoke rims that can be bought for around $35 and come already spoked and ready to use once a freewheel/cassette has been spun on. While people have commented on how much the rear wheel flexes while up on two wheels or during hard cornering, again, I have never had a failure and hear no spoke sounds that I would associate with problems. I have a small magnet-powered tail light that has the magnet mounted about 3/4" away from the light housing. When cornering hard at speed, the rear wheel definitely flexes enough for the magnet on the spokes to come in contact with the housing. I tried a 27" wheel and it was definitely not strong enough for trike use with the standard narrow hub. My friend and I are going to machine some custom x-long 36h hubs and make a couple "triple 27"" race trikes. I don't know what your planned loading is going to be, but I have build enough trikes like this and put enough KM on them to have pretty much 100% confidence in the BMX wheels, the standard plain-Jane 26" wheels (36 hole) and the mild steel axle housings. Hope this helps. Post pics when it's done I really must work on how I word things and be explicitly specific I am looking for a good guess (if not exact numbers) of the maximum side load a bike wheel (preferably a cheap 20" bmx wheel) can take before becoming a pretzel (i.e catastrophic failure and or but not including warping). This includes but is not limited to (ha-ha) nuts, washers, axel, axel bearings, bearing keepers, hub, spokes (likely 32 in total), spoke nipples (32 to match previous item), rim, rim rubber band to keep the nipples from the tube, tube (if used, if not strike last comments, preferably a standard tube not a shrader valve tube), and tire (preferably a slick as it is a road bike). One more thing, I will be using 14mm and above size axles before this deviates us from the current question leading us into many many debates on stuff other than the question at hand. What I am trying to do here is design a frame (trike) and on the rear axel (two wheels on this axel, maybe a bad choice of words here again 'on the rear weldment assembly, which are attached 2 axels') figure out the necessary strength of the rear weldment assembly. These wheels (on the rear weldment assembly) do not lean, they will be vertical at all times and should I hit a turn at a high rate of speed. I know approximately how many G's I generate on this said high rate of speed turn, I want to know how much the wheel will take before warping. I then will take this data and build the frame to take the side load the wheel can, using appropriate safety factors. Before I get a lecture on the theories on design and that I may be over my head in this, I am a experienced aircraft designer and have FEA and CFD tools to help me in this venture as well as experience in doing the calcs by hand. I am not trying to be smart here I just want to be specific so I can find out a resource of side loading capabilities of a bike wheel or how to calculate it without having to rig up a test and determine it my self. |
#8
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Max side load of a 20 inch rim?
Mark South wrote:
"Ben" wrote in message news:7s0Ac.45932$eA.1307@clgrps13... I really must work on how I word things and be explicitly specific I am looking for a good guess (if not exact numbers) of the maximum side load a bike wheel (preferably a cheap 20" bmx wheel) can take before becoming a pretzel (i.e catastrophic failure and or but not including warping). ... I am not trying to be smart here I just want to be specific so I can find out a resource of side loading capabilities of a bike wheel or how to calculate it without having to rig up a test and determine it my self. For most wheels the correct spoke tension is slightly above 100 kg force. Somewhat above this loading the rim cannot correctly support the loads and crinkles. If the load is uneven across spokes the spokes can pull through the hub flange. The spokes themselves do not break until considerably higher loadings are reached. See The Book for more detail. So: take your intended wheel, count the spokes and measure the spoke angle from flange to rim. Simple trig will show you how much tension there is to support the rim against a side load. I'd expect that a 48-spoke BMX wheel with a wide hub would withstand side loads at least as well as anything else commonly encountered in the bike world. The author of "The Book" has a well known preference for ISO 622-mm size Mavic MA-2 36-spoke rims with double butted spokes. I would suspect that a smaller diameter, wide, heavy duty rim (e.g. ISO 406-mm Sun Rhyno-Lite or Velocity Taipan) could withstand higher spoke tension before exhibiting a "potato chip" failure. Another approach would be to copy what works. Established trike builders such as Greenspeed use wheels such as I have mentioned above with good results. Unless you are attempting to achieve minimum weight, refinement through analysis and testing is not needed. The heavier stronger wheel will of course provide a larger factor of safety for occasional extreme dynamic loading that may occur. -- Tom Sherman – Quad City Area |
#9
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Max side load of a 20 inch rim?
"Ben" wrote in message news:7s0Ac.45932$eA.1307@clgrps13... I really must work on how I word things and be explicitly specific I am looking for a good guess (if not exact numbers) of the maximum side load a bike wheel (preferably a cheap 20" bmx wheel) can take before becoming a pretzel (i.e catastrophic failure and or but not including warping). This includes but is not limited to (ha-ha) nuts, washers, axel, axel bearings, bearing keepers, hub, spokes (likely 32 in total), spoke nipples (32 to match previous item), rim, rim rubber band to keep the nipples from the tube, tube (if used, if not strike last comments, preferably a standard tube not a shrader valve tube), and tire (preferably a slick as it is a road bike). One more thing, I will be using 14mm and above size axles before this deviates us from the current question leading us into many many debates on stuff other than the question at hand. What I am trying to do here is design a frame (trike) and on the rear axel (two wheels on this axel, maybe a bad choice of words here again 'on the rear weldment assembly, which are attached 2 axels') figure out the necessary strength of the rear weldment assembly. These wheels (on the rear weldment assembly) do not lean, they will be vertical at all times and should I hit a turn at a high rate of speed. I know approximately how many G's I generate on this said high rate of speed turn, I want to know how much the wheel will take before warping. I then will take this data and build the frame to take the side load the wheel can, using appropriate safety factors. Before I get a lecture on the theories on design and that I may be over my head in this, I am a experienced aircraft designer and have FEA and CFD tools to help me in this venture as well as experience in doing the calcs by hand. I am not trying to be smart here I just want to be specific so I can find out a resource of side loading capabilities of a bike wheel or how to calculate it without having to rig up a test and determine it my self. Ben Ben, Have you considered asking the companies that make the wheels? Just a thought.... jd |
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